We are examining both temporal and spatial changes in protein tyrosine phosphorylation following fertilization of mouse eggs using an antibody that recognizes phosphotyrosine and a secondary rhodamine or fluorescein conjugated antibody. In addition, we are using primary antibodies that recognize specific acetylated isoforms of histone-H4 to determine temporal and spatial changes in these proteins during preimplantation development in the mouse. 8-31-96